8273550: Replace os::cgc_thread/pgc_thread with os::gc_thread

Reviewed-by: stefank, coleenp

src/hotspot/os/posix/os_posix.cpp

@@ -979,8 +979,7 @@ size_t os::Posix::get_initial_stack_size(ThreadType thr_type, size_t req_stack_s
                       _compiler_thread_min_stack_allowed);
     break;
   case os::vm_thread:
-  case os::pgc_thread:
-  case os::cgc_thread:
+  case os::gc_thread:
   case os::watcher_thread:
   default:  // presume the unknown thr_type is a VM internal
     if (req_stack_size == 0 && VMThreadStackSize > 0) {

src/hotspot/os/windows/os_windows.cpp

@@ -712,8 +712,7 @@ bool os::create_thread(Thread* thread, ThreadType thr_type,
       } // else fall through:
         // use VMThreadStackSize if CompilerThreadStackSize is not defined
     case os::vm_thread:
-    case os::pgc_thread:
-    case os::cgc_thread:
+    case os::gc_thread:
     case os::asynclog_thread:
     case os::watcher_thread:
       if (VMThreadStackSize > 0) stack_size = (size_t)(VMThreadStackSize * K);

src/hotspot/share/gc/shared/concurrentGCThread.cpp

@@ -35,7 +35,7 @@ ConcurrentGCThread::ConcurrentGCThread() :
     _has_terminated(false) {}
 
 void ConcurrentGCThread::create_and_start(ThreadPriority prio) {
-  if (os::create_thread(this, os::cgc_thread)) {
+  if (os::create_thread(this, os::gc_thread)) {
     os::set_priority(this, prio);
     os::start_thread(this);
   }

src/hotspot/share/gc/shared/workgroup.cpp

@@ -159,19 +159,13 @@ GangWorker* WorkGang::install_worker(uint worker_id) {
 }
 
 void WorkGang::add_workers(bool initializing) {
-  os::ThreadType worker_type;
-  if (are_ConcurrentGC_threads()) {
-    worker_type = os::cgc_thread;
-  } else {
-    worker_type = os::pgc_thread;
-  }
   uint previous_created_workers = _created_workers;
 
   _created_workers = WorkerManager::add_workers(this,
                                                 _active_workers,
                                                 _total_workers,
                                                 _created_workers,
-                                                worker_type,
+                                                os::gc_thread,
                                                 initializing);
   _active_workers = MIN2(_created_workers, _active_workers);
 

src/hotspot/share/runtime/os.hpp

@@ -441,8 +441,7 @@ class os: AllStatic {
 
   enum ThreadType {
     vm_thread,
-    cgc_thread,        // Concurrent GC thread
-    pgc_thread,        // Parallel GC thread
+    gc_thread,         // GC thread
     java_thread,       // Java, CodeCacheSweeper, JVMTIAgent and Service threads.
     compiler_thread,
     watcher_thread,